This invention relates to a process for the production of s-triazine prepolymers.
It is known that difunctional or polyfunctional cyanic acid esters can be polymerised to form high molecular weight polytriazines (DT-AS No. 1,190,184). The polymerisation reaction is highly exothermic and involves relatively heavy shrinkage, proceeding by way of a so-called "B-state" (Kunststoffe Vol.58, page 829 (1968)). This gives rise to various disadvantages, especially in terms of processing, for example into glass-fibre-reinforced mouldings and, for example, in terms of the dimensional stability of the mouldings thus obtained. In order to avoid the disadvantages involved in direct polymerisation, it has already been proposed to obtain prepolymers by stopping polymerisation by cooling after about 30 to 65% of the cyanic acid ester groups have reacted (British Patent No. 1,305,762).